In U.S. Pat. No. 3,877,392, assigned to the same assignee as the present application, an elastomeric seal member is attached to the lower inner ends of the outlet walls including a tail portion extending along the external surface of the outlet wall, and a depending head portion which is engaged by the gate in closed position and when the gate moves between open and closed position. The engagement of the seal with the gate provides frictional resistance to movement of the gate. This force is sufficient to wear out the head portion of the seal, and added opening and closing torque is required to overcome it. Furthermore, air and entrained lading can escape by displacing the head portion outwardly as shown in FIG. 2. Also lading can collect upon longitudinally extending supports for the gate as shown in FIG. 3 and below the closure lip for the gate as shown in FIG. 4. Thus the gate does not assume the properly closed position, as illustrated in FIGS. 3 and 4.
In U.S. Pat. No. 3,626,866 a hopper outlet is disclosed in which U shaped resilient metallic sealing strips are attached to the external surface of the lower inner ends of inclined outlet walls with one leg of the U shaped member attached to the hopper wall and the other leg engaged by an outlet gate in closed position. These metallic seals are disadvantageous because they are easily damaged and require special equipment to install new units. They are expensive and require a specially formed gate.
In U.S. Pat. No. 2,738,735 a gravity outlet gate is ramped into closed position by an inclined cam surface located below the inner edge of the inner outlet wall. The gate includes a slot located below the front outlet wall which allows the gate to be ramped upwardly into closed position by the inclined cam surface without abutting the support for the front outlet wall.